This proposal is submitted in response to PAR-00-072, the Integrated Preclinical/Clinical AIDS Vaccine Development Program, and is Project 3 of a PO1 entitled "HIV-1 Vaccines designed to Induce Mucosal Immunity" from Dr. Thomas Evans, University of California, Davis. As an integrated project within the PO1 proposal, a major goal of this study is to provide new information regarding the induction of mucosal T-cell responses in humans, both in chronic infection and following vaccination. Our specific aims are as follows: (1) Determine the frequency, specificity and phenotype of antigen-specific T cells in mucosal and peripheral sites in naturally infected hosts. (2) Determine the localization of virus specific T cells after mucosal influenza vaccination. (3) Determine the frequency and specificity of HIV-specific CTL in peripheral blood and mucosae following DNA/Sindbis vaccination. We hypothesis that (1) because mucosal tissues are an important site of viral replication, immune activation and CD4+ T-cell depletion, the frequency of antigen-specific T cells in these tissues may be significantly different from that in blood, and (2) because mucosal and peripheral compartments are anatomically distinct immune effector cells in these regions may differ in specificity, clonality and phenotype. We predict that the vector and route of administration will determine localization of antigen-specific T cells, and that intranasal immunization will induce responses in peripheral blood, intestinal and genital mucosae. The experiments outlined in this project will be closely linked to the human vaccine studies outlined in Project 4, and will be complemented by murine and primate immunology studies described in Projects 1 and 2. The studies described in this proposal will provide important new information regarding the induction of HIV-specific immune responses at mucosal surfaces.